The Sciences

Any Publicity is Good Publicity?

Cosmic VarianceBy JoAnne HewettFeb 28, 2006 3:03 AM


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Maybe in Hollywood, but not necessarily elsewhere.... I should have learned this in high school - then, the local newspaper did a feature each week highlighting a group of seniors from the various schools. There was a theme each week and the group answered questions on topic. I was chosen and was pretty excited about it - until the interview started and I learned the theme was religion. Being my honest, naive, 17-yr-old self, I stated that I was rather unsure about the existence of God and that I thought churches were money making organizations. Naturally, I was quoted in print. In a smaller midwestern town. I received a barrage of truly hateful mail - some letters acusing me of devil worship, others wanting to save my soul. My senior science teacher summed it up best by saying `What you said was probably correct, but it's not what you say to a newspaper reporter.' That's when I should have learned to be careful with reporters. Two weeks ago, it happened again. The good folks in the SLAC publicity office are starting a feature where every few weeks a piece of work from the SLAC theory group will be highlighted. Great idea, I thought! I was the first guinea pig and was asked to do an interview for an article on a paper I wrote last Spring. The work was cute, has a catchy title, and is published in Physical Review Letters, but is not going to change life on earth as we know it. The article was to be for the internal SLAC newsletter TIP (The Interaction Point) and would also make a brief appearance on SLAC Today, the daily newsboard for the SLAC community. So, co-author Tom Rizzo and I spent an hour with the reporter, we saw a draft of the article and sent in revisions, and they took a few pictures of us at the blackboard. We could not get too technical, we were told, because the article was intended for the general, non-scientific, SLAC community. Next thing I knew, the headline

SLAC Physicists Develop Test for String Theory

was emblazened on the main SLAC homepage! Then Peter Woit of Not Even Wrong lashed onto it. Then it was picked up by, which was subsequently featured by Slashdot. All with a smiling picture of yours truly, supposedly devising a definitive test for all of string theory. AARGH!!!! The entire article was misrepresented, blown up out of proportion, and I could not have been more upset. Nothing against the good folks at the communications office at SLAC - we worked on this together and none of us saw this coming. Nonetheless, I did not have a good week. The remedy? We posted comments on all the blogs and revised the article to include the scientific details which then put our work into proper context. So, what's all the fuss about? There has been heated discussion, on this blog and elsewhere, regarding the fact that there are no known scientific tests to prove or disprove the existence of string theory. We came up with an idea that could test classes of string theories, within a very particular framework, which may or may not be present in nature. If this framework exists, then we can test for whether there are 10 or 11 dimensions of spacetime, as Sean recently explained is favored by critical string theory, or not. Here is the revised version of the article:

SLAC Physicists Develop Framework-Dependent Test For Critical String Theory String theory solves many of the questions wracking the minds of physicists, but it has one major flaw â€" there are currently no known methods to test it. SLAC scientists have found a way to test a particular version of this revolutionary theory. The test applies to a class of critical string theories which posit that there are 10 or 11 dimensions in our universe â€" no more, no less. This past December, Joanne Hewett, Thomas Rizzo and student Ben Lillie published an article in Physical Review Letters which shows theoretically how to measure the number of dimensions that comprise the universe. By determining how many dimensions exist, Hewett, Lillie and Rizzo hope to either confirm or repudiate critical string theory under specific conditions. The first three dimensions, length, height and width, are familiar to all of us. The fourth dimension is time. But what are the extra dimensions? "Imagine a tightrope stretched between skyscrapers," says Hewett. "If you are watching an acrobat walk across it â€" the tightrope looks like a line. But if you are watching an ant walk on the tightrope, you can see that the tightrope is thick and round." The extra dimensions postulated in string theory are like the tightrope with an ant on it; they are too small to see unless you get really, really close. Hewett, Lillie and Rizzo found that if so called micro-black holes, which are smaller than the nucleus of an atom, exist, they can be used to determine the number of extra dimensions. If scientists were to smash two high energy protons together they could theoretically make such a micro-black hole. Such a collision could happen at CERN's Large Hadron Collider (LHC), which will become operational next year. Once created, the micro-black hole decays quickly and emits over a dozen different kinds of particles such as electrons, neutrinos and photons, which are easy to detect. Using the predicted decay properties of the black hole into neutrinos, Hewett, Lillie and Rizzo solved complex equations to determine if our universe has 10, 11, or more dimensions â€" perhaps too many dimensions to be explained by critical string theory. More technically, the analysis applies to models of extra dimensions where micro-black holes can be formed with a size smaller than the curvature of the additional dimensions and where the fundamental particles which make up our universe do not reside in the extra dimensions. These micro-black holes must also exist at an energy scale which can be probed at the LHC. Under those very specific conditions, the test holds. These conditions are possible within string theory, but need not be present. "The computations were so massive, we had to make extreme use of the Babar UNIX farm," said Rizzo. Of course, string theory hasn't been tested yet â€" experimental evidence is necessary. Additionally, Hewett, Lillie and Rizzo's analysis can only disprove critical string theory; it cannot prove it. "If they see black holes at the LHC, they'll definitely do this analysis," says Hewett. "This would tell us about the fundamental nature of the universe."

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